When an underlayer material is etched by using a photoresist as a mask, an etching selectivity between the photoresist and the underlayer material becomes insufficient and a process becomes difficult in some cases. Hence, there is a method for patterning a metal film by using a photoresist as a mask and etching an underlayer material by using this metal film as a mask. The mask of this metal film is referred to as a hard mask.
Using dry etching to form a hard mask increases manufacturing cost of a semiconductor device. This is because the dry etching is a vacuum process, and therefore a throughput is low and process cost is high. Therefore, it is preferable to form a hard mask by using wet etching of a higher throughput and more reasonable process cost than dry etching.
As semiconductor devices are scaled-down, scaling-down of hard mask patterns is also demanded. The wet etching is isotropic etching, and therefore there is generally a significant pattern conversion difference between a photoresist mask and a pattern to be formed. It is desired to realize a method for forming a fine metal pattern which suppresses a pattern conversion difference between the metal pattern and a photoresist mask to scale down a hard mask pattern.